BMW OBC Anti-Theft Code E23, E24, E28, E30, E32, E34, E36

This answer is applicable for many BMWs in addition to the one listed below.

Q
car year: 1988
car model: 325i Convertible
I just got my second BMW. It is a 325i 1988 convertible. This afternoon I went to a place to have it cleaned inside, but I do not know what happened. When I try to turn it on, the horn starts beeping and the main computer ask for a code (?) and the car does not start. Without starting the car, I turn on the main switch and the computer ask for a code. If I type any combination of numbers the horn starts beeping again for 30 seconds, and then stops, waiting for another code. What should I do? I cannot use my car.

A
The ’80s and ’90s BMW models (E23, E24, E28, E30, E32, E34, E36) that have the separate On Board Computer units (OBC), such as your E30 chassis (3 series 84-91), have an anti-theft feature available within the OBC. If this feature is activated, the pre-set 4-digit code must be input. When activated, the starter will turn, but the engine will not start. After 3-attempts, the horn will sound for 30-seconds.

It’s likely that the people doing the cleaning, accidentally activated the anti-theft by pushing the OBC CODE button while the key was in the #1 position (perhaps listening to the radio). They may have just been lucky enough to push the buttons in the sequence that ended up storing a code and activating the system.

The owner’s manual for your 325ic gives the sequence and instruction for activating, using and de-activating the system, but there is no mention of what to do in case you “forget” the code you input. However, the owner’s manual for a later model E34 chassis (5 series 89-96) does mention an emergency procedure for the system (which is similar to your 325ic). So, give it a try. If this does not work (remember, it is for a different model), try just disconnection the battery for 15-minutes, or so. If this also does not work, we can tell you how to by-pass the system, by cutting and splicing the wires for the anti-theft module.

Do you mean that your OBC anti-theft feature has been activated and you do not know (or recall) what the code is?

If the system has been activated, but the code is not known, here’s the emergency start procedure for the E36 models (3-series 92-99):

* Disconnect the battery for 5-minutes, then reconnect.
* Turn ignition key to the 1st position – The alarm will sound and the time (in the OBC display) will count down 15 minutes (15 to zero).
* After 15 minutes, the engine can be started.

If you need the radio code:
The only way to get the radio code (if you have no records of what it is), is to remove the radio, write down the radio serial number (on a sticker on the radio chassis), and have a BMW dealer look up the code.